Semiconductor device and method of manufacturing the same

ABSTRACT

A semiconductor device includes a first active structure on a substrate including a first epitaxial pattern, a second epitaxial pattern and a first channel pattern between the first epitaxial pattern and the second epitaxial pattern, the first channel pattern including at least one channel pattern stacked on the substrate. A first gate structure is disposed on top and bottom surfaces of the first channel pattern. A second active structure on the substrate and includes the second epitaxial pattern, a third epitaxial pattern and a second channel pattern between the second epitaxial pattern and the third epitaxial pattern in the first direction. The second channel pattern includes at least one channel pattern stacked on the substrate. The number of stacked second channel patterns is greater than the number of stacked first channel patterns. A second gate structure is disposed on top and bottom surfaces of the second channel pattern.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/230,656, filed on Dec. 21, 2018, which claims priority to U.S. patentapplication Ser. No. 15/295,115, filed on Oct. 17, 2016, to KoreanPatent Application No. 10-2016-0022949 filed on Feb. 26, 2016 in theKorean Intellectual Property Office, the disclosures of which areincorporated by reference herein in their entirety.

1. TECHNICAL FIELD

Exemplary embodiments of the present inventive concept relate to asemiconductor device and a method of manufacturing the same.

2. DISCUSSION OF RELATED ART

Highly integrated semiconductor devices may include a high performancetransistor. Highly integrated semiconductor devices may also includevarious types of transistors having different electricalcharacteristics.

SUMMARY

According to an exemplary embodiment of the present inventive concept, asemiconductor device includes a first active structure on a substrateand including a first epitaxial pattern, a second epitaxial pattern anda first channel pattern between the first epitaxial pattern and thesecond epitaxial pattern in a first direction parallel to a top surfaceof the substrate, the first channel pattern including at least twochannel patterns stacked on the substrate. A first gate structure isdisposed on top and bottom surfaces of the first channel pattern andextends in a second direction perpendicular to the first direction andparallel to the top surface of the substrate. A second active structureon the substrate and includes the second epitaxial pattern, a thirdepitaxial pattern and a second channel pattern between the secondepitaxial pattern and the third epitaxial pattern in the firstdirection. The second channel pattern includes at least one channelpattern stacked on the substrate. The number of stacked second channelpatterns is greater than the number of stacked first channel patterns. Asecond gate structure is disposed on top and bottom surfaces of thesecond channel pattern and extends in the second direction.

According to an exemplary embodiment of the present inventive concept, asemiconductor device includes a first active structure on a substrateand including a first epitaxial pattern, a second epitaxial pattern anda first channel pattern between the first epitaxial pattern and thesecond epitaxial pattern in a first direction parallel to a top surfaceof the substrate, the first channel pattern including at least onechannel pattern stacked on the substrate. A first gate structure isdisposed on top and bottom surfaces of the first channel pattern andextends in a second direction perpendicular to the first direction andparallel to the top surface of the substrate. A second active structureis on the substrate and includes a third epitaxial pattern, a fourthepitaxial pattern and a second channel pattern between the thirdepitaxial pattern and the fourth epitaxial pattern in the firstdirection. The second channel pattern includes at least one channelpattern stacked on the substrate. The number of stacked second channelpatterns is greater than the number of stacked first channel patterns. Asecond gate structure is disposed on top and bottom surfaces of thesecond channel pattern and extends in the second direction. A dummyactive structure is on the substrate. The dummy active structureincludes the second epitaxial pattern, the third epitaxial pattern, adummy channel pattern between the second epitaxial pattern and the thirdepitaxial pattern in the first direction. The dummy channel patternincludes at least one channel pattern stacked on the substrate. A dummygate structure is disposed on top and bottom surfaces of the dummychannel pattern and extends in the second direction.

According to an exemplary embodiment of the present inventive concept, asemiconductor device includes a plurality of epitaxial patterns, on asubstrate, that are spaced apart from each other in a first directionparallel to a top surface of the substrate. A plurality of channelpattern groups is between the plurality of epitaxial patterns in thefirst direction. Each of the plurality of channel pattern groupsincludes a plurality of channel patterns stacked in a second directionperpendicular to the top surface of the substrate. At least one channelpattern group of the plurality of channel pattern groups has a firstnumber of channel patterns different from a second number of channelpatterns included in another channel pattern group of the plurality ofchannel pattern groups. A plurality of gate structures is on theplurality of the channel pattern groups, respectively. Each of theplurality of gate structures extends in a third direction perpendicularto the first direction and parallel to the top surface of the substrate.Each of the plurality of gate structures is disposed on top and bottomsurfaces of the plurality of channel patterns of each of the pluralityof channel pattern groups.

According to an exemplary embodiment of the present inventive concept, amethod of manufacturing a semiconductor device includes forming a firstsemiconductor structure in which first semiconductor patterns and firstchannel patterns are alternately and repeatedly stacked on a substrate.The first semiconductor structure has a first number of stacked firstchannel patterns. The method includes forming a second semiconductorstructure in which second semiconductor patterns and second channelpatterns are alternately and repeatedly stacked on the substrate. Thesecond semiconductor structure has a second number of stacked secondchannel patterns different from the first number of stacked firstchannel patterns. The first semiconductor structure is spaced apart fromthe second semiconductor structure in a first direction parallel to atop surface of the substrate. A first epitaxial pattern is formed on afirst sidewall of the first semiconductor structure. A second epitaxialpattern is formed on a second sidewall of the first semiconductorpattern and a first sidewall of the second semiconductor pattern. Athird epitaxial pattern is formed on a second sidewall of the secondsemiconductor structure. The first and second semiconductor patterns offirst and second semiconductor structures are selectively removed. Afirst gate structure is formed on top and bottom surfaces of the firstchannel patterns of the first semiconductor structure extending in asecond direction perpendicular to the first direction and parallel tothe top surface of the substrate. A second gate structure is formed ontop and bottom surfaces of the second channel patterns of the secondsemiconductor structure extending in the second direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are a cross-sectional view and a plan view illustratinga semiconductor device according to an exemplary embodiment of thepresent inventive concept;

FIG. 2 is a cross-sectional view illustrating an active structure in asemiconductor device according to an exemplary embodiment of the presentinventive concept;

FIGS. 3 through 27 are perspective views, plan views and cross-sectionalviews illustrating a semiconductor device according to an exemplaryembodiment of the present inventive concept;

FIG. 28 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 29 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 30 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 31 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 32 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 33 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIG. 34 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept;

FIGS. 35 through 37 are cross-sectional views illustrating a method ofmanufacturing a semiconductor device according to an exemplaryembodiment of the present inventive concept; and

FIG. 38 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Various exemplary embodiments of the present inventive concept will bedescribed more fully hereinafter with reference to the accompanyingdrawings, in which some exemplary embodiments are shown. The presentinventive concept may, however, be embodied in many different forms andshould not be construed as limited to the exemplary embodiments setforth herein.

FIGS. 1A and 1B are a cross-sectional view and a plan view illustratinga semiconductor device according to an exemplary embodiment of thepresent inventive concept. FIG. 2 is a cross-sectional view illustratingan active structure in a semiconductor device according to an exemplaryembodiment of the present inventive concept.

Referring to FIGS. 1A, 1B and 2 , a first transistor 10 and a secondtransistor 12 that have different electrical characteristics from eachother may be disposed on a substrate 100. The first transistor 10 andthe second transistor 12 may be disposed adjacent to each other in afirst direction parallel to a top surface of the substrate 100. In someexemplary embodiments, the first and second transistors 10 and 12 mayshare one impurity region. In some exemplary embodiments, the secondtransistor 12 may have a relatively higher operating current compared tothe first transistor 10.

The substrate 100 may include a semiconductor material such as silicon,germanium or silicon-germanium, or a III-V group compound semiconductor.

A first active structure 20 included in the first transistor 10 and asecond active structure 22 included in the second transistor 12 may bedisposed on the substrate 100. A portion of the first and second activestructures 20 and 22 may be shared. In other words, the first and secondactive structures 20 and 22 may be in contact with each other in thefirst direction and may form one active structure 170. The first activestructure 20 may include a first epitaxial pattern 148 a, a secondepitaxial pattern 148 b and a first channel pattern 132 between thefirst and second epitaxial patterns 148 a and 148 b. The first andsecond epitaxial patterns 148 a and 148 b may act as source/drainregions of the first transistor 10. The first and second epitaxialpatterns 148 a and 148 b may be disposed on opposite sides of the firstchannel pattern 132 in the first direction. The first and secondepitaxial pattern 148 a and 148 b may be in direct contact with the topsurface of the substrate 100 on opposite sides of the first channelpattern 132.

The first channel pattern 132 may include a plurality of channelpatterns between the first and second epitaxial patterns 148 a and 148b. The plurality of first channel patterns 132 may be spaced apart fromeach other in a third direction perpendicular to the top surface of thesubstrate 100. The first channel patterns 132 may be spaced apart fromthe top surface of the substrate 100. Channels may be formed inrespective ones of the first channel patterns 132. In some exemplaryembodiments, the first channel pattern 132 may include one channelpattern between the first and second epitaxial patterns 148 a and 148 b.

The first channel patterns 132 may include two channel patterns;however, exemplary embodiments of the present inventive concept are notlimited thereto. For example, the first channel patterns 132 may includethree or more channel patterns.

In some exemplary embodiments, the first channel patterns 132 may eachhave substantially the same thickness in third direction. In otherexemplary embodiments, at least one of the first channel patterns 132may have a different thickness from the other first channel patterns 132in the third direction.

Referring to FIG. 2 , a plurality of first tunnels 139 a may be formedbetween the first channel patterns 132. The first channel patterns 132may be spaced apart from each other by the plurality of first tunnels139 a. The number of the first tunnels 139 a may increase as the numberof the first channel patterns 132 increases.

The first and second epitaxial patterns 148 a and 148 b may be dopedwith impurities to act as the source/drain regions. The first channelpatterns 132 may be doped with impurities of an opposite conductive typeto the first and second epitaxial patterns 148 a and 148 b.

A first gate structure 166 a acting as a gate of the first transistor 10may be positioned on the first active structure 20. The first gatestructure 166 a may surround the first channel patterns 132 and mayextend in a second direction parallel to the top surface of thesubstrate and perpendicular to the first direction.

The first gate structure 166 a may include a first gate insulatingpattern 154 a, a first gate electrode 162 a and a first hard mask 164 athat are stacked.

The first gate electrode 162 a may include a first lower gate pattern162 a 1 and a first upper gate pattern 162 au. The first lower gatepattern 162 a 1 may be disposed in the plurality of first tunnels 139 a,and the first upper gate pattern 162 au may be disposed on a top surfaceof an uppermost one of the first channel patterns 132. The first lowerand upper gate patterns 162 a 1 and 162 au may be integrally connectedto each other at regions between the first active structures 20 in thesecond direction.

The gate insulating pattern 154 a may be disposed between the first gateelectrode 162 a and the first channel patterns 132. The first hard mask164 a may be disposed on the first upper gate pattern 162 au.

The first gate insulating pattern 154 a may be positioned on surfaces ofthe plurality of first tunnels 139 a. The first gate insulating pattern154 a may be positioned on side and bottom surfaces of the first uppergate pattern 162 au.

The first gate insulating pattern 154 a may include a metal oxide havinga high dielectric constant. For example, the first gate insulatingpattern 154 a may include hafnium oxide (HfO₂), tantalum oxide (Ta₂O₅)and/or zirconium oxide (ZrO₂).

The first gate 162 a may include a first threshold voltage controlpattern and a first metal pattern. The first threshold voltage controlpattern may directly contact the first gate insulating pattern 154 andmay have a work function depending on a desired threshold voltage of thefirst transistor 10. In some exemplary embodiments, the first thresholdvoltage control pattern may include titanium, titanium nitride and/ortitanium aluminum nitride. The first metal pattern may include a metal,such as aluminum (Al), copper (Cu) or tantalum (Ta), and/or a metalnitride thereof.

The first hard mask 164 may include silicon nitride.

A first spacer 128 may be disposed on opposite sidewalls of the firstupper gate pattern 166 au. The first spacer 128 may be disposed on thetop surface of the uppermost one of the first channel patterns 132. Thefirst spacer 128 may be disposed on opposite sidewalls of the first gatestructure 166 a at the regions between the first active structures 20.The first spacer 128 may include, for example, silicon nitride.

A second spacer 144 may disposed between the first lower gate pattern166 a 1 and the first epitaxial pattern 148 a and between the firstlower gate pattern 166 a 1 and the second epitaxial pattern 148 b. Thesecond spacer 144 may include an insulating material. For example, thesecond spacer 144 may include silicon oxide.

The second active structure 22 may include the second epitaxial pattern148 b, a third epitaxial pattern 148 c and a second channel pattern 134between the second epitaxial pattern 148 b and the third epitaxialpattern 148 c.

The second and third epitaxial patterns 148 b and 148 c may act assource/drain regions of the second transistor 12. The second and thirdepitaxial patterns 148 b and 148 c may be disposed on opposite sides ofthe second channel pattern 134 in the first direction. The secondepitaxial pattern 148 b may be commonly used by the first and secondactive structures 20 and 22.

The second and third epitaxial patterns 148 b and 148 c may be in directcontact with the substrate 100 and may contact opposite ends of thesecond channel pattern 134, respectively.

The second channel pattern 134 may include a plurality of channelpatterns between the second epitaxial pattern 148 b and the thirdepitaxial pattern 148 c. The plurality of second channel patterns 134may be spaced apart from each other in the third direction. In someexemplary embodiments, the second channel patterns 134 may be spacedapart from the top surface of the substrate 100.

The number of the second channel patterns 134 stacked in the thirddirection may be different from the number of the first channel patterns132 stacked in the third direction. The number of stacked second channelpatterns 134 may be greater than the number of stacked first channelpatterns 132. Thus, an operating current of the second transistor 12 maybe greater than the operating current of the first transistor 10.

In some exemplary embodiments, the second channel patterns 134 may eachhave substantially the same thickness in the third direction.Alternatively, at least one of the second channel patterns 134 may havea different thickness from the other second channel patterns 134 in thethird direction.

In some exemplary embodiments, each of the second channel patterns 134may be substantially parallel to each of the first channel patterns 132at respective position levels. The first and second channel patterns 132and 134 positioned at the same position level may have substantially thesame thickness in the third direction.

In some exemplary embodiments, the second channel patterns 134 might notbe arranged parallel to the first channel patterns 132 at respectiveposition levels. In other exemplary embodiments, the second channelpatterns 134 and the first channel patterns 132 may be arranged to bepositioned at different position levels. At least one of the secondchannel patterns 134 may have a different thickness from the firstchannel patterns 132 in the third direction.

A plurality of second tunnels 139 b may be formed between the secondchannel patterns 134. Thus, adjacent second channel patterns 134 may bespaced apart from each other by a respective one of the plurality ofsecond tunnels 139 b. In some exemplary embodiments, the number of thesecond tunnels 139 b may be greater than the number of the first tunnels139 a.

The second and third epitaxial patterns 148 a and 148 c may be dopedwith impurities to act as the source/drain regions. The second channelpatterns 134 may be doped with impurities of an opposite conductive typeto the second and third channel patterns 148 b and 148 c.

A second gate structure 166 b acting as a gate of the second transistor12 may be positioned on the second active structure 22. The second gatestructure 166 b may surround the second channel patterns 134 and mayextend in the second direction.

The second gate structure 166 b may include a second gate insulatingpattern 154 b, a second gate electrode 162 b and a second hard mask 164b that are stacked.

The second gate electrode 162 b may include a second lower gate pattern162 b 1 and a second upper gate pattern 162 bu. The second lower gatepattern 162 b 1 may be disposed in the second tunnels 139 b and mayextend in the second direction. The second upper gate pattern 162 bu maybe disposed on a top surface of an uppermost one of the second channelpatterns 134 and may extend in the second direction. The second lowerand upper gate patterns 162 b 1 and 162 bu may be integrally connectedto each other in regions between the second active structures 22 in thesecond direction.

In some exemplary embodiments, a top surface of the second upper gatepattern 162 bu may be substantially coplanar with a top surface of thefirst upper gate pattern 162 au. Thus, a thickness of the first uppergate pattern 162 au in the third direction may be greater than that ofthe second upper gate pattern 162 bu in the third direction.

A second gate insulating pattern 154 b may be disposed between thesecond gate electrode 162 b and the second channel patterns 134. Asecond hard mask 164 b may be disposed on the second upper gate pattern162 bu.

The second gate insulating pattern 154 b may be formed on a surface ofthe second lower gate pattern 162 b 1. The second gate insulatingpattern 154 b may be formed on side and bottom surfaces of the secondupper gate pattern 162 bu.

The second gate insulating pattern 154 b may include a metal oxidematerial having a relatively high dielectric constant. For example, thesecond gate insulating pattern 154 b may include hafnium oxide, tantalumoxide and/or zirconium oxide.

In some exemplary embodiments, the first and second gate insulatingpatterns 154 a and 154 b may include substantially the same material.

The second gate electrode 162 b may include a second threshold voltagecontrol pattern and a second metal pattern. The second threshold voltagecontrol pattern may directly contact the second gate insulating pattern154 b and may have a work function depending on a desired thresholdvoltage of the second transistor 12. The second metal pattern mayinclude a metal, such as aluminum (Al), copper (Cu) or tantalum (Ta),and/or metal nitride thereof. In some exemplary embodiments, the secondgate electrode 162 b may include substantially the same material as thefirst gate electrode 162 a.

The first spacer 128 may be disposed on opposite sidewalls of the secondupper gate pattern 162 bu. The first spacer 128 may be disposed on thetop surface of the uppermost one of the second channel patterns 134. Thefirst spacer 128 may be disposed on opposite sidewalls of the secondgate structure 166 b at the regions between the second active structures22.

The second spacer 144 may be disposed between the second lower gatepattern 162 b 1 and the second epitaxial pattern 148 b and between thesecond lower gate pattern 162 b 1 and the third epitaxial pattern 148 c.

In some exemplary embodiments, more than one active structures 170 maydisposed on the substrate 100.

The active structures 170 may be positioned adjacent to each other inthe second direction. The first epitaxial patterns 148 a in therespective active structures 170 may be electrically connected to eachother in the second direction. The second epitaxial patterns 148 b inthe respective active structures 170 may be connected to each other inthe second direction. The third epitaxial patterns 148 c in therespective active structures 170 may be connected to each other in thesecond direction. In some exemplary embodiments, the first through thirdepitaxial patterns 148 a, 148 b and 148 c may extend in the seconddirection.

A first insulating interlayer 150 may be disposed on the first throughthird epitaxial patterns 148 a, 148 b and 148 c and may fill a gapbetween the first and second gate structures 166 a and 166 b. The firstinsulating interlayer 150 may include, for example, silicon oxide.

In some exemplary embodiments, an insulating liner layer 149 may beconformally disposed on sidewalls of the first and second gatestructures 166 a and 166 b and on top surfaces of the first throughthird epitaxial patterns 148 a, 148 b and 148 c. The insulating liner149 may include silicon nitride.

A second insulating interlayer 174 may be disposed on the firstinsulating interlayer 150. The second insulating interlayer 174 mayinclude, for example, silicon oxide.

First through third contact plugs 176 a, 176 b and 176 c may passthrough the first and second insulating interlayers 150 and 174 and theinsulating liner layer 149. The first contact plug 176 a, the secondcontact plug 176 b and the third contact plug 176 c may contact thefirst epitaxial pattern 148 a, the second epitaxial pattern 148 b andthe third epitaxial pattern 148 c, respectively.

The first and second transistors 10 and 12 may include different numbersof channel patterns, and thus the electrical characteristics of thefirst and second transistors 10 and 12 may be different from each other.The first and second transistors 10 and 12 may be disposed adjacent eachother and may share one impurity region.

The first and second transistors 10 and 12 adjacent each other may beformed on the same number of active structures 170 in the seconddirection. Thus, when the first and second transistors 10 and 12 areformed, a removing process of the active structure formed on some areasmight not be needed. Thus, a variation in an effective area of theactive structure by a removal of the active structure need not begenerated, and thus electrical characteristics of the transistors neednot be changed.

An additional pattern for device isolation need not be disposed betweenthe first and second transistors 10 and 12. Thus, the first and secondtransistors 10 and 12 having the different electrical characteristicsmay be formed in a relatively narrow area.

FIGS. 3 through 27 are perspective views, plan views and cross-sectionalviews illustrating a semiconductor device according to an exemplaryembodiment of the present inventive concept.

FIGS. 3 through 6 and 8 are perspective views, FIGS. 9, 11, 13, 15through 17, 19 through 21, 23, 24, 26 and 27 are cross-sectional views,and FIGS. 7, 10, 12, 14, 18, 22 and 35 are plan views.

Referring to FIG. 3 , a first semiconductor layer 102 and a secondsemiconductor layer 104 may be alternately and repeatedly stacked on asubstrate 100 such that a first preliminary semiconductor structure 105is formed.

The substrate 100 may include a semiconductor material such as silicon,germanium or silicon-germanium, or a III-V group compound semiconductor.In an exemplary embodiment, the substrate 100 may be a bulk siliconsubstrate.

The substrate 100 may include a first region in which a first transistoris formed and a second region in which a second transistor is formed.

The first semiconductor layer 102 may define regions in which the firstand second gate patterns will be formed, and the second semiconductorlayer 104 will be formed to be first and second channel patterns. Thus,the second semiconductor layer 104 may have substantially the samethickness as a desired thickness of the first and second channelpatterns.

The first and second semiconductor layers 102 and 104 may each include asingle crystal semiconductor material having an etching selectivity withrespect to each other. In some exemplary embodiments, the firstsemiconductor layer 102 may include a single crystal silicon germanium,and the second semiconductor layer 104 may include a single crystalsilicon. The first and second semiconductor layers 102 and 104 may beformed by an epitaxial growth process. In some exemplary embodiments,when the second semiconductor layer 104 is formed, impurities may bedoped in-situ such that a channel doping process of the first and secondtransistors may be conducted.

The first semiconductor layers 102 may be formed to have substantiallythe same thickness. The second semiconductor layers 104 may be formed tohave substantially the same thickness. In some exemplary embodiments, atleast one of the second semiconductor layers 104 may be formed to have adifferent thickness from the other second semiconductor layers 104.

In some exemplary embodiments, an uppermost layer of the firstpreliminary semiconductor structure 105 may be a second semiconductorlayer 104 of the semiconductor layers 104. In the first preliminarysemiconductor structure 105, the number of stacked second semiconductorlayers 104 may be the same as the number of second channel patterns(e.g., the second channel patterns 134) included in the secondtransistor (e.g., the second transistor 12).

Referring to FIG. 4 , a portion of the first and second semiconductorlayers 102 and 104 in the first region may be etched. Thus, a secondpreliminary semiconductor structure 105 a having a step in the first andsecond regions may be formed.

An etching mask that substantially covers a top surface of the firstpreliminary semiconductor structure 105 in the second region may beformed. The first and second layers 102 and 104 of the first preliminarysemiconductor structure 105 in the first region may be partiallysequentially etched using the etching mask such that the secondpreliminary structure 105 a is formed.

In the second preliminary structure 105 a, the number of stacked secondsemiconductor layers 104 in the first region may be the same as thenumber of first channel patterns (e.g., the first channel patterns 132)included the first transistor (e.g., the first transistor 10). Anuppermost layer of the second preliminary semiconductor structure 105 ain the first region may be a second semiconductor layer 104 of thesecond semiconductor layers 104 in the first region.

The etching mask may be removed.

Referring to FIG. 5 , a hard mask 106 may be formed on the secondpreliminary semiconductor structure 105 a and may be patterned by aphotolithography and etch process to form the hard mask 106. The hardmask 106 may have a linear shape that extends in the first direction. Insome exemplary embodiments, a plurality of hard masks 106 may be formedand may be arranged in the second direction.

The hard mask 106 may include silicon nitride.

Referring to FIGS. 6 and 7 , the second preliminary semiconductorstructure 105 a may be sequentially etched using the hard mask 106 as anetch mask, and then an upper portion of the substrate 100 may be etched.Thus, a first semiconductor structure 118 may be formed on the substrate100 and may include a first semiconductor layer 112 and a secondsemiconductor layer 114 alternately and repeatedly stacked. A deviceisolation trench may be formed in the substrate 100. The firstsemiconductor structure 118 may extend in the first direction.

A device isolation layer may be formed on the substrate 100, and then anupper portion of the device isolation layer may be removed. Thus, adevice isolation pattern 101 may be formed in the device isolationtrench. The first semiconductor structure 118 may be disposed betweenthe first device isolation patterns 101 and may protrude above thedevice isolation pattern 101. The device isolation pattern 101 mayinclude, for example, silicon oxide.

Referring to FIG. 6 , the first semiconductor structure 118 may beformed in one semiconductor structure. Alternatively, referring to FIG.7 , a plurality of first semiconductor structures 118 may be formed andeach of the plurality of first semiconductor structures 118 may extendin the second direction.

A portion of the first semiconductor structure 118 in the first regionmay be referred to as a first portion of the first semiconductorstructure 118, and another portion of the first semiconductor structure118 in the second region may be referred to as a second portion of thefirst semiconductor structure 118.

Referring to FIGS. 8 through 10 , first and second mold gate structures126 a and 126 b that extend in the second direction may be formed on thefirst semiconductor structure 118 and the device isolation pattern 101.

A mold gate insulating layer and a mold gate layer may be formed on thefirst semiconductor structure 118 and the device isolation pattern 101.

The mold gate insulating layer may include, for example, silicon oxide.The mold gate insulating layer may be formed by, for example, a chemicalvapor deposition (CVD) process, an atomic layer deposition (ALD) processor a thermal oxidation process. The mold gate layer may include, forexample, poly-silicon. The mold gate layer may be formed by, forexample, an ALD process or a CVD process. After the mold gate layer isformed, a planarization process may be performed such that a top surfaceof the mold gate layer is planarized.

A hard mask layer may be formed on the mold gate layer and may bepatterned by a photolithography and etching process, thereby forming ahard mask 124. The hard mask 124 may extend in the second direction. Thehard mask 124 may cover a region in which the first and second gatestructures of the first and second transistors are formed by a followingprocess. Thus, the hard mask 124 may include at least one hard maskdisposed on each of the first and second portions of the firstsemiconductor structure 118.

The mold gate layer and the mold gate insulating layer may besequentially anisotropically etched using the hard mask 124 as an etchmask. Thus, the first mold gate structure 126 a that includes a firstmold gate insulating pattern 120 a, a first mold gate pattern 122 a andthe hard mask 124 may be formed in the first region of the substrate100. The second mold gate structure 126 b that includes a second moldgate insulating pattern 120 b, a second mold gate pattern 122 b and thehard mask 124 may be formed in the second region of the substrate 100.The first and second mold gate structures 126 a and 126 b may definerespective regions in which first and second gate structures of thefirst and second transistors will be formed.

The first mold gate structure 126 a may be in direct contact with thedevice isolation pattern 101 and a sidewall and a top surface of thefirst portion of the first semiconductor structure 118 and may extend inthe second direction. The second mold gate structure 126 b may be indirect contact with the device isolation pattern 101 and a sidewall anda top surface of the second portion of the first semiconductor structure118 and may extend in the second direction.

The top surfaces of the first and second mold gate patterns 122 a and122 b may be substantially coplanar. Thus, a height of the second moldgate pattern 122 b from the top surface of the first semiconductorstructure 118 may be greater than that of the first mold gate pattern122 a from the top surface of the first semiconductor structure 118.

Regions illustrated as dashed lines in FIG. 9 may represent “A” portionsof the first and second mold gate patterns illustrated in FIG. 8

Referring to FIGS. 11 and 12 , a first spacer 128 may be formed onsidewalls of the first and second mold gate structures 126 a and 126 b.

A first spacer layer may be conformally formed on the first and secondmold gate structures 126 a and 126 b, the device isolation pattern 101and the first semiconductor structure 118. The first spacer layer mayinclude an insulating material, for example, silicon nitride. The firstspacer layer may be formed by, for example, a CVD process or an ALDprocess. The first spacer layer may be anisotropically etched such thatthe first spacer 128 is formed on the sidewalls of the first and secondmold gate structures 126 a and 126 b.

Referring to FIGS. 13 and 14 , the first semiconductor structure 118exposed between the first spacers 128 may be etched to form a secondsemiconductor structure 118 a in the first region and a thirdsemiconductor structure 118 b in the second region. An opening 140exposing the substrate 100 may be formed between the second and thirdsemiconductor structures 118 a and 118 b.

The second semiconductor structure 118 a may include a structure inwhich the first preliminary semiconductor patterns 113 and first channelpatterns 132 are alternately stacked, and the third semiconductorstructure 118 b may include a structure in which the first preliminarysemiconductor patterns 113 and second channel patterns 134 arealternately stacked. The number of stacked second channel patterns 134may be greater than the number of stacked first channel patterns 132.

In the second and third semiconductor structures 118 a and 118 b,opposite sidewalls of the first preliminary semiconductor patterns 113and the first and second channel patterns 132 and 134 may be exposed.

Referring to FIG. 15 , the opposite sidewalls of the first preliminarysemiconductor patterns 113 exposed in the second and third semiconductorstructures 118 a and 118 b may be selectively etched to a predetermineddepth in the first direction such that recesses 142 are formed. By theetching process, the second and third semiconductor structure 118 a and118 b may respectively form first and second active structures 136 and138.

The etching process may include an isotropic etching process, forexample, a wet etching process or an isotropic dry etching process.

The first preliminary semiconductor patterns 113 may form firstsemiconductor patterns 130 of which a width in the first direction isdecreased, through the etching process. In the etching process, thefirst and second channel patterns 132 and 134 need not be etched, andthus the first and second channel patterns 132 and 134 may furtherprotrude in the first direction with respect to the first semiconductorpatterns 130.

Referring to FIG. 16 , a second spacer 144 may be formed on sidewalls ofthe first semiconductor patterns 130 and may fill the recesses 142. Thesecond spacer 144 may include an insulating material, for example,silicon oxide.

A second spacer layer may be conformally formed on the first and secondmold gate structures 126 a and 126 b, the substrate 100, the deviceisolation pattern 101 and the first and second channel patterns 132 and134. The second spacer layer may be formed to fill the recesses 142formed on the sidewalls of the first semiconductor patterns 130. Thesecond spacer layer may be formed by, for example, a CVD process or anALD process. Since the second spacer layer may be formed along surfacesof the first and second mold gate structures 126 a and 126 b, thesubstrate 100, the device isolation pattern 101 and the first and secondchannel patterns 132 and 134, in the deposition process, a portion ofthe second spacer layer formed in the recesses 142 may be formed thickerthan other portions of the second spacer layer.

The second spacer layer formed on the first and second mold gatestructures 126 a and 126 b, the substrate 100, the device isolationpattern 101 and the first and second channel patterns 132 and 134 may beremoved such that the second spacer 144 filling the recesses 142 isformed on the sidewalls of the first semiconductor patterns 130. In someexemplary embodiments, the second spacer layer may be removed by a wetetching process or a wet cleaning process.

Referring to FIGS. 17 and 18 , first, second and third epitaxialpatterns 148 a, 148 b and 148 c may be formed on the substrate 100exposed at opposite sides of the first and second mold gate structures126 a and 126 b. The first and second epitaxial patterns 148 a and 148 bmay be formed at the opposite sides of the first mold gate structure 126a, respectively. The second and third epitaxial patterns 148 b and 148 cmay be formed at the opposite sides of the second mold gate structure126 b, respectively.

The first channel patterns 132 may be disposed between the firstepitaxial pattern 148 a and the second epitaxial patterns 148 b.Opposite sidewalls of the first channel patterns 132 may be in directcontact with the first and second epitaxial patterns 148 a and 148 b.

The second channel patterns 134 may be disposed between the secondepitaxial pattern 148 b and the third epitaxial pattern 148 c. Oppositesidewalls of the second channel patterns 134 may be in direct contactwith the second and third epitaxial patterns 148 b and 148 c. Thus, thefirst through third epitaxial patterns 148 a, 148 b and 148 c and thefirst and second channel patterns 132 and 134 may be connected in thefirst direction.

The first through third epitaxial patterns 148 a, 148 b and 148 c mayproject in the second direction. Thus, the first through third epitaxialpatterns 148 a, 148 b and 148 c may be respectively connected to eachother on the device isolation pattern 101. The first epitaxial patterns148 a may be connected to each other in the second direction. The secondepitaxial patterns 148 b may be connected to each other in the seconddirection, and the third epitaxial patterns 148 c also may be connectedto each other in the second direction. Thus, the first through thirdepitaxial patterns 148 a, 148 b and 148 c may extend in the seconddirection.

The first through third epitaxial patterns 148 a, 148 b and 148 c may beformed by performing a selective epitaxial growth (SEG) process usingthe surfaces of the exposed substrate 100 and the first and secondchannel patterns 132 and 134 as a seed.

In some exemplary embodiments, the first through third epitaxialpatterns 148 a, 148 b and 148 c may include silicon or silicongermanium.

In some exemplary embodiments, when performing the epitaxial growthprocess, impurities may be doped in-situ. Thus, the first through thirdepitaxial patterns 148 a, 148 b and 148 c may act as source/drainregions of the first and second transistors.

In some exemplary embodiments, after forming the first through thirdepitaxial patterns 148 a, 148 b and 148 c, an impurity doping processand an annealing process may be further be performed to form thesource/drain regions.

The second epitaxial pattern 148 b may be disposed between the firstmold gate structure 126 a and the second mold gate structure 126 b.Thus, the second epitaxial pattern 148 a may be provided as a commonimpurity region of the first and second transistor.

Top surfaces of the first through third epitaxial patterns 148 a, 148 band 148 c may be higher than uppermost ones of the first and secondchannel patterns 132 and 134.

Referring to FIG. 19 , an insulating liner layer 149 may be conformallyformed on the first through third epitaxial patterns 148 a, 148 b and148 c, the first and second gate structures 126 a and 126 b and thefirst spacer 128. In some exemplary embodiments, the insulating linerlayer 149 may act as an etching stopper. The insulating liner layer 149may include, for example, silicon nitride.

A first insulating interlayer 150 may be formed on the insulating linerlayer 149 and may fill a space between the first and second mold gatestructures 126 a and 126 b. The first insulating interlayer 150 mayinclude, for example, silicon oxide.

Referring to FIG. 20 , upper portions of the first insulating interlayer150, the hard mask 124, the insulating liner layer 149 and the firstspacer 128 may be planarized until the top surfaces of the first andsecond mold gate patterns 122 a and 122 b are exposed. The planarizationprocess may include a chemical mechanical polishing process and/or anetch-back process.

By performing the planarization process, the hard mask 124 may besubstantially completely removed. An upper portion of each of the firstinsulating interlayer 150, the insulating liner layer 149 and the firstspacer 128 may be partially removed.

Referring to FIGS. 21 and 22 , the first and second mold gate patterns122 a and 122 b and the first and second mold gate insulating patterns120 a and 120 b may be removed to form first and second openings 152 aand 152 b, respectively.

The first opening 152 a may extend in the second direction whileexposing a top surface and sidewalls of the first preliminary activestructure 136. In the first opening 152 a, a top surface of theuppermost one of the first channel patterns 132, inner sidewalls of thefirst spacer 128 and opposite sidewalls of the first channel patterns132 and the first semiconductor patterns 130 may be exposed.

The second opening 152 b may extend in the second direction whileexposing a top surface and sidewalls of the second preliminary activestructure 138. In the second opening 152 b, a top surface of theuppermost one of the second channel patterns 134, inner sidewalls of thefirst spacer 128 and opposite sidewalls of the second channel patterns134 and the first semiconductor patterns 130 may be exposed.

Referring to FIG. 23 , the first semiconductor patterns 130 in the firstand second preliminary active structures 136 and 138 may be selectivelyremoved.

The first semiconductor patterns 130 may be removed by an isotropicetching process. Thus, the first channel patterns 132 may be spacedapart from each other in the third direction, and first tunnels 139 amay be formed between the first channel patterns 132. The second channelpatterns 134 may be spaced apart from each other in the third direction,and second tunnels 139 b may be formed between the second channelpatterns 134.

Thus, an active structure 170 that includes a first active structure 20,which may be used to form the first transistor and a second activestructure 22, which may be used to form the second transistor, may beformed. The first active structure 20 may include the first and secondepitaxial patterns 148 a and 148 b and a stack of the first channelpatterns 132 disposed between the first and second epitaxial patterns148 a and 148 b. The second active structure 22 may include the secondand third epitaxial patterns 148 b and 148 c and a stack of the secondchannel patterns 134 between the second and third epitaxial patterns 148b and 148 c. The number of stacked second channel patterns 134 may begreater than that of stacked first channel patterns 132.

Referring to FIGS. 24 and 25 , a first preliminary gate structure 160 aand a second preliminary gate structure 160 b may be formed to fill thefirst opening 152 a and the second opening 152 b, respectively.

A gate insulating layer may be conformally formed on the first spacer128 exposed in the first and second openings 152 a and 152 b, the firstand second channel pattern 132 and 134, the second spacer 144, thedevice isolation pattern 101 and the first insulating interlayer 150.The gate insulating layer may include a metal oxide material having ahigher dielectric constant than silicon nitride. The gate insulatinglayer may include, for example, hafnium oxide (HfO₂), tantalum oxide(Ta₂O₅) and zirconium oxide (ZrO₂).

A gate electrode layer may be formed on the gate insulating layer andmay substantially completely fill the first and second openings 152 aand 152 b.

In some exemplary embodiments, the gate electrode layer may include athreshold voltage control layer and a metal layer. The threshold voltagecontrol layer may be in direct contact with the gate insulating layerand may have a work function depending on a desired threshold voltage ofthe transistor.

In some exemplary embodiments, the threshold voltage control layer mayinclude titanium, titanium nitride and/or titanium aluminum nitride. Thework function may be controlled by a combination of metals included inthe threshold voltage control layer. The metal layer may include, forexample, metal such as aluminum (Al), copper (Cu) or tantalum (Ta)and/or metal nitride thereof.

The gate electrode layer and the gate insulating layer may be planarizeduntil the top surface of the first insulating interlayer 150 is exposed,such that the first and second preliminary gate structures 160 a and 160b may be formed in the first and second openings 152 a and 152 b,respectively.

The first preliminary gate structure 160 a may include a first gateinsulating pattern 154 a and a first preliminary gate electrode 156 a,and the second preliminary structure 160 b may include a second gateinsulating pattern 154 b and a second preliminary gate electrode 156 b.

Referring to FIG. 26 , the first and second preliminary electrodes 156 aand 156 b positioned in the upper portion of the first and secondopenings 152 a and 152 b may be partially etched to form first andsecond gate electrode 162 a and 162 b. A hard mask layer filling theetched portions may be formed and then may be planarized to form firstand second hard masks 164 a and 164 b.

Thus, a first gate structure 166 a, in which the first gate insulatingpattern 154 a, the first gate electrode 162 a and the first hard mask164 a are stacked, may be formed on the first active structure 20. Asecond gate structure 166 b, in which the second gate insulating pattern154 b, the second gate electrode 162 b and the second hard mask 164 bare stacked, may be formed on the second active structure 22.

The first gate electrode 162 a may include a first lower gate pattern162 a 1 formed in the first tunnels 139 a and a first upper gate pattern162 au formed on the uppermost one of the first channel patterns 132.The second gate electrode 162 b may include a second lower gate pattern162 b 1 formed in the second tunnels 139 b and a second upper gatepattern 162 bu formed on the uppermost one of the second channelpatterns 134.

Thus, the first transistor 10 including the first active structure 20and the first gate structure 166 a and the second transistor 20including the second active structure 22 and the second gate structure166 b may be formed.

Referring to FIG. 27 , a second insulating interlayer 174 may be formedon the first insulating interlayer 150 and the first and second gatestructures 166 a and 166 b.

The second insulating interlayer 174 may include, for example, siliconoxide and may be formed by a chemical vapor deposition process.

First through third contact plugs 176 a, 176 b and 176 c may be formedto penetrate the second insulating interlayer 174 and to contact thefirst through epitaxial patterns 148 a, 148 b and 148 c, respectively.

The formation of the first through third contact plugs 176 a, 176 b and176 c may include etching a portion of the second insulating interlayer174 to form first through third contact holes that expose the topsurfaces of the first through third epitaxial patterns 148 a, 148 b and148 c, respectively, forming a conductive layer in the first throughthird contact holes and planarizing the conductive layer.

The first through third contact plugs 176 a, 176 b and 176 c may be indirect contact with the impurity regions of the first and secondtransistors 10 and 12. The second contact plug 176 b may be in directcontact with the common impurity region of the first and secondtransistors 10 and 12.

According to an exemplary embodiment of the present inventive concept,the first and second transistors (e.g., the first transistor 10 and thesecond transistor 12) that have different electrical characteristicsfrom each other may be adjacent each other on the substrate (e.g., thesubstrate 100). Since the first and second transistors may includedifferent numbers of the channel patterns from each other, the first andsecond transistors may have different electrical characteristics fromeach other. For example, since the second transistor may include arelatively larger number of the channel patterns than that of the firsttransistor, the second transistor may have a relatively high operatingcurrent characteristics compared to the first transistor.

FIG. 28 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

The semiconductor device may be substantially the same as thesemiconductor device described with reference to FIGS. 1A, 1B and 2except that the substrate is a silicon-on-insulator (SOI) substrate or asilicon germanium-on-insulator (SGOI) substrate, and thus duplicativedescriptions may be omitted.

Referring to FIG. 28 , the substrate 100 may include a semiconductorlayer 100 c in an upper part of the substrate 100 and an insulatinglayer 100 b under the semiconductor 100 c in the substrate 100. Thesubstrate 100 may include a bulk substrate 100 a under the insulatinglayer 100 b in the substrate 100. In some exemplary embodiments, thesubstrate 100 may be an SOI substrate in which the semiconductor layer100 c includes single crystal silicon and the insulating layer 100 bincludes silicon oxide. The semiconductor device described in moredetail above with reference to FIGS. 1A, 1B and 2 may be disposed on thesubstrate 100.

FIG. 29 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.FIG. 30 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

Referring to FIG. 29 , first and second transistors 10 and 12 that aredifferent from each other in an electrical characteristic may bedisposed on a substrate 100. A dummy transistor 14 may be disposedbetween the first transistor 10 and the second transistor 12. A firstimpurity region of the dummy transistor 14 may be a second impurityregion of the first transistor 10, and a second impurity region of thedummy transistor 14 may be a first impurity region of the secondtransistor 12.

In some exemplary embodiments, the substrate 100 may include asemiconductor material such as silicon, germanium or silicon-germanium,or a III-V group compound semiconductor.

In some exemplary embodiments, the substrate 100 may be asilicon-on-insulator (SOI) substrate or a silicon germanium-on-insulator(SGOI) substrate. The substrate 100 may include a semiconductor materiallayer as a part of an upper portion thereof and an insulating materiallayer under the semiconductor material layer.

A first active structure, which may be used to form the first transistor10 and a second active structure, which may be used to form the secondtransistor 12, may be disposed on the substrate 100. A dummy activestructure, which may be used to form the dummy transistor 14, may bedisposed between the first active structure and the second activestructure. Thus, the first and second active structures may be spacedapart from each other in the first direction.

The first active structure, the dummy active structure and the secondactive structure may be connected to each other and may extend in thefirst direction, thus forming one active structure 170 a. In someexemplary embodiments, a plurality of active structures 170 a may bearranged in the second direction. Channel patterns in each of the activestructures 170 a may be respectively arranged adjacent to each other inthe second direction.

The first active structure may include a first epitaxial pattern 148 a,a second epitaxial pattern 148 b and a plurality of first channelpatterns 132 between the first epitaxial pattern 148 a and the secondepitaxial pattern 148 b. The first and second epitaxial patterns 148 aand 148 b may act as the first and second impurity regions (e.g.,source/drain regions) of the first transistor 10. The first activestructure may be substantially the same as the first active structure 20described in more detail with reference to FIGS. 1A, 1B and 2 .

The first transistor 10 formed on the first active structure may besubstantially the same as the first transistor 10 described in moredetail with reference to FIGS. 1A, 1B and 2 . The first gate structure166 a formed on the first active structure may be substantially the sameas the first gate structure 166 a described in more detail withreference with FIGS. 1A, 1B and 2 .

The second active structure may include a third epitaxial pattern 148 c,a fourth epitaxial pattern 148 d and a plurality of second channelpatterns between the third epitaxial pattern 148 c and the fourthepitaxial pattern 148 d. The third epitaxial pattern 148 c may be spacedapart from the second epitaxial pattern 148 b in the first direction.The third and fourth epitaxial patterns 148 c and 148 d may act as thefirst and second impurity regions (e.g., source/drain regions) of thesecond transistor 12.

The epitaxial patterns of the first and second active structures neednot be shared. The second active structure may be substantially the sameas the second active structure 22 described in more detail withreference to FIGS. 1A, 1B and 2 except that the second structure doesnot share the second epitaxial pattern with the first active structure.

The second transistor 12 formed on the second active structure may besubstantially the same as the second transistor 12 described in moredetail with reference to FIGS. 1A, 1B and 2 . The second gate structure166 b formed on the second active structure may be substantially thesame as the second gate structure 166 b described in more detail withreference to FIGS. 1A, 1B and 2 .

In some exemplary embodiments, the number of stacked second channelpatterns 134 in the third direction may be different from the number ofstacked first channel patterns 132 in the third direction. In someexemplary embodiments, the number of stacked second channel patterns 134may be greater than the number of stacked first channel patterns 132.

Thus, the number of the channel patterns of the second transistor 12 maybe greater than the number of the channel patterns of the firsttransistor 10. An operating current of the second transistor 12 may begreater than an operating current of the first transistor 10.

The dummy active structure may include the second epitaxial pattern 148b, the third epitaxial pattern 148 c and a plurality of dummy channelpatterns 180 between the second epitaxial pattern 148 b and the thirdepitaxial pattern 148 c. In some exemplary embodiments, the number ofstacked dummy channel patterns 180 may be the same as the number ofstacked second channel patterns 134. In some exemplary embodiments, theshape of the dummy channel patterns 180 may be substantially the same asthe shape of the second channel patterns 134.

The dummy active structure may share the second epitaxial pattern 148 band the third epitaxial pattern 148 c with the first active structureand the second active structure.

A dummy gate structure 166 c may surround the dummy channel patterns 180and may extend in the second direction. The dummy gate structure 166 cmay include a dummy gate insulating pattern 154 c, a dummy gateelectrode 162 c and a third hard mask 164 c.

In some exemplary embodiments, the dummy gate structure 166 c may besubstantially the same as the second gate structure 166 b.

In some exemplary embodiments, referring to FIG. 30 , the number ofstacked dummy channel patterns 180 may be the same as the number ofstacked first channel patterns 132; and the shape of the dummy channelpatterns 180 may be the same as the shape of the first channel patterns132. In this case, the dummy gate structure 166 c may be substantiallythe same as the first gate structure 166 a.

Top surfaces of the first and second gate structures 166 a and 166 b maybe substantially coplanar with a top surface of the dummy gate structure166 c.

The dummy transistor 14 may be disposed between the first transistor 10and the second transistor 12 and need not substantially perform aswitching operation.

A first contact plug 176 a and a second contact plug 176 b may be indirect contact with the first epitaxial pattern 148 a and the secondepitaxial pattern 148 b, respectively.

A third contact plug 176 c and a fourth contact plug 176 d may be indirect contact with the third epitaxial pattern 148 c and the fourthepitaxial pattern 148 d, respectively.

FIG. 31 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

Referring to FIG. 31 , first and second transistors 10 and 12 that aredifferent from each other in an electrical characteristic may bedisposed on a substrate 100. The first and second transistors 10 and 12may be adjacent each other. In some exemplary embodiments, the first andsecond transistors 10 and 12 may share one impurity region.

In some exemplary embodiments, the substrate 100 may include asemiconductor material such as silicon, germanium or silicon-germanium,or a III-V group compound semiconductor.

In some exemplary embodiments, the substrate 100 may be asilicon-on-insulator (SOI) substrate or a silicon germanium-on-insulator(SGOI) substrate. The substrate 100 may include a semiconductor materiallayer as a part of an upper portion thereof and an insulating materiallayer under the semiconductor material layer.

A first active structure may be used to form a first transistor and asecond active structure may be used to form a second transistor. Aportion of the second active structure may be shared with the firstactive structure.

The first and second active structures may be connected to each other,thereby forming one active structure 170. In some exemplary embodiments,a plurality of active structures 170 may be arranged in the seconddirection. Channel patterns of the active structures 170 may berespectively arranged adjacent to each other in the second direction.

The first active structure may include a first epitaxial pattern 148 a,a second epitaxial pattern 148 b and first channel patterns 132 betweenthe first epitaxial pattern 148 a and the second epitaxial pattern 148b. The first channel patterns 132 may include a plurality of channelpatterns that are spaced apart from each other in the third direction.In some exemplary embodiments, each of the first channel patterns 132may have substantially the same first thickness as each other in thethird direction.

The first transistor 10 formed on the first active structure may besubstantially the same as the first transistor 10 described in moredetail with reference to FIGS. 1A, 1B and 2 . A first gate structure 166a formed on the first active structure may be substantially the same asthe first gate structure 166 a described in more detail with referenceto FIGS. 1A, 1B and 2 .

The second active structure may include a second epitaxial pattern 148b, a third epitaxial pattern 148 c and a plurality of second channelpatterns 134 and 134 a disposed between the second epitaxial pattern 148b and the third epitaxial pattern 148 c.

The second channel patterns 134 and 134 a may be spaced apart from eachother in the third direction. A number of stacked second channelpatterns 134 and 134 a in the third direction may be different from thenumber of stacked first channel patterns 132 in the third direction. Insome exemplary embodiments, the number of stacked second channelpatterns 134 and 134 a in the third direction may be greater than thenumber of stacked first channel patterns 132 in the third direction.

At least one of the second channel patterns 134 and 134 a may have adifferent thickness from the other second channel patterns 134 and 134a. In some exemplary embodiments, an uppermost one 134 a of the secondchannel patterns 134 and 134 a may have a different thickness from theother second channel patterns 134. For example, the second channelpatterns 134 under the uppermost second channel pattern 134 a may have afirst thickness in the third direction, and the uppermost second channelpattern 134 a may have a second thickness greater than the firstthickness.

The second transistor 12 formed on the second active structure may besubstantially the same as the second transistor 12 described in moredetail with reference to FIGS. 1A, 1B and 2 . A second gate structure166 b formed on the second active structure may be substantially thesame as the second gate structure 166 b described in more detail withreference to FIGS. 1A, 1B and 2 .

First through third contact plugs 176 a, 176 b and 176 c may be indirect contact with the first through third epitaxial patterns 148 a,148 b and 148 c, respectively.

The first and second transistors 10 and 12 may have different electricalcharacteristics due to different stack numbers and different thicknessesof the channel patterns.

The semiconductor device may be manufactured by performing substantiallythe same processes as those described in more detail with reference toFIGS. 3 through 27 . However, when forming the first preliminarysemiconductor structure, a thickness of the second semiconductor layermay be controlled depending on the thicknesses of the first and secondchannel patterns. For example, the uppermost second semiconductor layermay be formed thicker than the second semiconductor layers under theuppermost second semiconductor layer, and thus the semiconductor deviceshown in FIG. 31 may be manufactured.

FIG. 32 is a cross-sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

Referring to FIG. 32 , first and second transistors 10 and 12 havingdifferent electrical characteristics may be disposed on a substrate 100.A dummy transistor 14 may be disposed between the first and secondtransistors 10 and 12. A first impurity region of the dummy transistor14 may be a second impurity region of the first transistor 10, and asecond impurity region of the dummy transistor 14 may be a firstimpurity region of the second transistor 12.

A first active structure, which may be used to form the first transistor10 and a second active structure, which may be used to form the secondtransistor 12 may be disposed on the substrate 100. A dummy activestructure may be disposed between the first and second activestructures. Thus, the first active structure and the second activestructure may be spaced apart from each other in the first direction.

The first active structure, the dummy active structure and the secondactive structure may be connected to each other and may extend in thefirst direction, thereby forming one active structure 170 a. In someexemplary embodiments, a plurality of the active structure 170 a may bearranged parallel to each other in the second direction. Channelpatterns in the active structures 170 a may be respectively arrangedadjacent to each other in the second direction.

The first active structure may include a first epitaxial pattern 148 a,a second epitaxial pattern 148 b and a plurality of first channelpatterns 132 between the first epitaxial pattern 148 a and the secondepitaxial pattern 148 b. The first and second epitaxial patterns 148 aand 148 b may act as the first and second impurity regions (e.g.,source/drain regions) of the first transistor 10. The first activestructure may be substantially the same as the first active structure 20described in more detail with reference to FIGS. 1A, 1B and 2 .

The first transistor 10 that is formed on the first active structure maybe substantially the same as the first transistor 10 described in moredetail with reference to FIGS. 1A, 1B and 2 .

The second active structure may include a third epitaxial pattern 148 c,a fourth epitaxial pattern 148 d and a plurality of second channelpatterns 134 and 134 a disposed between the third epitaxial pattern 148c and the fourth epitaxial pattern 148 d. The third epitaxial pattern148 c may be spaced apart from the second epitaxial pattern 148 b in thefirst direction. The third and fourth epitaxial patterns 148 c and 148 dmay act as the first and second impurity regions (e.g., source/drainregions) of the second transistor 12.

The epitaxial patterns of the first and second active structures neednot be shared. However, the second active structure may be substantiallythe same as the second active structure described with reference to FIG.31 except that the second epitaxial pattern is not shared.

In some exemplary embodiments, the number of stacked second channelpatterns 134 and 134 a in the third direction may be different from thenumber of stacked first channel patterns 132 in the third direction. Insome exemplary embodiments, the number of stacked second channelpatterns 134 and 134 a may be greater than the number stacked firstchannel patterns 132.

At least one of the second channel patterns 134 and 134 a may have adifferent thickness from the other second channel patterns 134 and 134a. For example, the first channel patterns 132 and the second channelpatterns 134 under an uppermost second channel pattern 134 a mayrespectively have a first thickness. Also, the uppermost second channelpattern 134 a may have a second thickness greater than the firstthickness.

The second transistor 12 formed on the second active structure may besubstantially the same as the second transistor 12 described in moredetail with reference to FIGS. 1A, 1B and 2 .

The dummy active structure may include the second epitaxial pattern 148b, the third epitaxial pattern 148 c and dummy channel patterns 180 and180 a disposed between the second epitaxial pattern 148 b and the thirdepitaxial pattern 148 c. In some exemplary embodiments, the number ofdummy channel patterns 180 and 180 a may be the same as the number ofsecond channel patterns 134 and 134 a. The dummy channel patterns 180and 180 a corresponding to the respective second channel patterns 134and 134 a at a same position level may have substantially the samethickness as the second channel patterns 134 and 134 a.

The dummy active structure may share the second and third epitaxialpatterns 148 b and 148 c with the first and second active structures.

A dummy gate structure 166 c may surround the dummy channel patterns 180and 180 a and may extend in the second direction. The dummy gatestructure 166 c may include a dummy gate insulating pattern 154 c, adummy gate electrode 162 c and a third hard mask 164 c.

In some exemplary embodiments, the dummy gate structure 166 c may besubstantially the same as a second gate structure 166 b. The second gatestructure 166 b may be substantially the same as the second gatestructure 166 b described in more detail with reference to FIGS. 1A, 1Band 2 .

In other exemplary embodiments, the number of dummy channel patterns 180and 180 a may be the same as the number of first channel patterns 132.In this case, the dummy gate structure 166 c may be substantially thesame as a first gate structure 166 a. The first gate structure 166 a maybe substantially the same as the first gate structure 166 a described inmore detail with reference to FIGS. 1A, 1B and 2 .

Top surfaces of the first and second gate structures 166 a and 166 b maybe substantially coplanar with a top surface of the dummy gate structure166 c.

The dummy transistor 14 may be disposed between the first transistor 10and the second transistor 12 and need not substantially perform aswitching operation.

A first contact plug 176 a and a second contact plug 176 b may be indirect contact with the first epitaxial pattern 148 a and the secondepitaxial pattern 148 b, respectively. A third contact plug 176 c and afourth contact plug 176 d may be in direct contact with the thirdepitaxial pattern 148 c and the fourth epitaxial pattern 148 d,respectively.

FIG. 33 is a cross sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.FIG. 34 is a cross sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

Referring to FIG. 33 , a semiconductor device according to an exemplaryembodiment of the present inventive concept may be substantially thesame as that the semiconductor device described with reference to FIGS.1A, 1B and 2 except that a first gate insulating pattern and a secondgate insulating pattern include different materials.

Referring to FIG. 33 , a first transistor 10 and a second transistor 12may respectively include the first gate insulating pattern 184 a and thesecond gate insulating pattern 184 b that include different materials.Thus, the first and second transistors 10 and 12 may have differentelectrical characteristics.

In some exemplary embodiments, the first transistor 10 and the secondtransistor 12 may include different numbers of stacked channel patterns(e.g. the number of stacked first channel patterns 132 and the number ofstacked second channel patterns 134 may be different from each other)

In some exemplary embodiments, the first and second transistors 10 and12 may include the same number of stacked channel patterns (e.g. thenumber of stacked first channel patterns 132 and the number of stackedsecond channel patterns 134 may be equal to each other)

FIGS. 35 through 37 are cross sectional views illustrating a method ofmanufacturing a semiconductor device according to an exemplaryembodiment of the present inventive concept.

Active structures may be formed by performing the processes described inmore detail with reference to FIGS. 3 through 23 .

Referring to FIG. 35 , a first mask pattern 182 may be formed to coverthe active structure in the second region.

A first gate insulating layer 184 may be conformally formed on the firstactive structure, the first and second spacers 128 and 144, the firstinsulating interlayer 150 and the first mask pattern 182 that are formedin the first region. The first gate insulating layer 184 may include afirst metal oxide material having a relatively high dielectric constant.The first gate insulating layer 184 may include hafnium oxide (HfO₂),tantalum oxide (Ta₂O₅) and/or zirconium oxide (ZrO₂).

Referring to FIG. 36 , the first mask pattern 182 may be removed. Thefirst gate insulating layer 184 on the first mask pattern 182 may alsobe removed. Accordingly, the first gate insulating layer 184 may beconformally formed on surfaces of the first channel patterns 132, thefirst and second spacers 128 and 144 and the first insulating interlayer150.

A second mask pattern 186 may be formed to cover the active structure inthe second region.

A second gate insulating layer 188 may be conformally formed on thesecond active structure, the first and second spacers 128 and 144, thefirst insulating interlayer 150 and the second mask pattern 186 that areformed in the second region. The second insulating layer 188 may includea second metal oxide material different from the first metal oxidematerial.

Referring to FIG. 37 , the second mask pattern 186 may be removed. Thesecond gate insulating layer 188 on the second mask pattern 188 may alsobe removed. Thus, the second gate insulating layer 188 may beconformally formed on surfaces of the second channel patterns 134, thefirst and second spacers 128 and 144 and the first insulating interlayer150.

A gate electrode layer may be formed on the first and second gateinsulating layers 184 and 188 to fill the first and second openings 152a and 152 b. The gate electrode layer and the first and second gateinsulating layers 184 and 188 may be planarized to expose a top surfaceof the first insulating interlayer 150 such that first and secondpreliminary gate structures 160 a and 160 b may be formed in the firstand second gate openings 152 a and 152 b, respectively. The first andsecond preliminary gate structures 160 a and 160 b may include first andsecond gate insulating patterns 184 a and 188 a, respectively.

The semiconductor device described in more detail with reference to FIG.32 may be manufactured by performing substantially the same processes asdescribed in more detail with reference to FIGS. 26 and 27 .

FIG. 38 is a cross sectional view illustrating a semiconductor deviceaccording to an exemplary embodiment of the present inventive concept.

Referring to FIG. 38 , the semiconductor device according to anexemplary embodiment of the present inventive concept may include firstand second transistors 10 and 12 that have different electricalcharacteristics and are formed on a substrate 100. The semiconductordevice may include a dummy transistor 14 that is formed on the substrate100 between the first transistor 10 and the second transistor 12.

For example, the first and second transistors 10 and 12 may besubstantially the same as the first and second transistors 10 and 12described in more detail with reference to FIG. 34 . The first andsecond transistors 10 and 12 may include the same number of stackedchannel patterns as each other. A first gate insulating pattern 184 aand a second gate insulating pattern 184 b may include differentmaterials.

In some exemplary embodiments, the dummy transistor 14 may besubstantially the same as the first transistor 10. In this case, a dummygate insulating pattern 190 of the dummy transistor 14 may include thesame material as the first gate insulating pattern 184 a. In someexemplary embodiments, the dummy transistor 14 may be substantially thesame as the second transistor 12. In this case, the dummy gateinsulating pattern 190 of the dummy transistor 14 may include the samematerial as the second gate insulating pattern 188 a.

In some exemplary embodiments, the first and second transistors 10 and12 may be substantially the same as the first and second transistors 10and 12 described with reference to FIG. 33 . The first and secondtransistors 10 and 12 may include different numbers of stacked channelpatterns from each other. In the first and second transistors 10 and 12,the first and second gate insulating patterns 184 a and 188 a mayinclude different materials. In this case, the dummy transistor 14 maybe substantially the same as the first transistor 10 or the secondtransistor 12.

The semiconductor device according to exemplary embodiments of thepresent inventive concept may include transistors that have differentelectrical characteristics and are disposed immediately adjacent to eachother. The adjacent transistors can respectively have desired electricalcharacteristics without affecting each other. A dummy gate or aseparation pattern such as a device isolation pattern might not beincluded between the transistors having different electricalcharacteristics, and thus a space between the transistors can bereduced. Thus, the semiconductor device according to exemplaryembodiments of the present inventive concept may be highly integrated.

The semiconductor device according to exemplary embodiments of thepresent inventive concept may be applied to a memory device or a logicdevice.

While the present inventive concept has been particularly shown anddescribed with reference to exemplary embodiments thereof, it will beunderstood by those of ordinary skill in the art that various changes inform and details may be made therein without departing from the spiritand scope of the present inventive concept.

What is claimed is:
 1. A semiconductor device, comprising: a substrate;a first transistor, wherein the first transistor comprises: a pluralityof first channel patterns stacked on the substrate, wherein adjacentchannel patterns of the plurality of first channel patterns areseparated by a first gate insulating pattern and first and secondspacers disposed on opposite sides, respectively, of the first gateinsulating pattern; a second transistor, wherein the second transistorcomprises: a plurality of second channel patterns stacked on thesubstrate, wherein adjacent channel patterns of the plurality of secondchannel patterns are separated by a second gate insulating pattern andthird and fourth spacers disposed on opposite sides, respectively, ofthe second gate insulating pattern; a first epitaxial pattern disposedon a first sidewall of the first transistor; a second epitaxial patterndisposed on a second sidewall of the first transistor and a firstsidewall of the second transistor; and a third epitaxial patterndisposed on a second sidewall of the second transistor, wherein thesecond epitaxial pattern are shared by the first transistor and thesecond transistor, and wherein a first number of the stacked firstchannel patterns is different from a second number of the stacked secondchannel patterns, and wherein at least one of the plurality of firstchannel patterns and at least one of the plurality of second channelpatterns have substantially a same thickness in a directionsubstantially perpendicular to a top surface of the substrate.
 2. Thesemiconductor device according to claim 1, wherein the first gateinsulating pattern surrounds a first lower gate pattern disposed betweenthe first and second spacers, and wherein the second gate insulatingpattern surrounds a second lower gate pattern disposed between the thirdand fourth spacers.
 3. The semiconductor device according to claim 2,wherein the first transistor further comprises a first upper gatepattern disposed above an uppermost one of the stacked first channelpatterns, and wherein the second transistor further comprises a secondupper gate pattern disposed above an uppermost one of the stacked secondchannel patterns.
 4. The semiconductor device according to claim 3,further comprising: fifth and sixth spacers on opposite sidewalk,respectively, of the first upper gate pattern; and seventh and eighthspacers on opposite sidewalls, respectively, of the second upper gatepattern.
 5. The semiconductor device according to claim 4, wherein thefirst to fourth spacers include an oxide, and the fifth to eighthspacers include a nitride.
 6. The semiconductor device according toclaim 1, further comprising a first contact plug contacting the firstepitaxial pattern, a second contact plug contacting the second epitaxialpattern and a third contact plug contacting the third epitaxial pattern.7. The semiconductor device according to claim 1, wherein each of theplurality of first channel patterns and each of the plurality of secondchannel patterns have substantially a same thickness in a directionperpendicular to a top surface of the substrate.
 8. The semiconductordevice according to claim 1, wherein at least one of the plurality offirst channel patterns has a different thickness from a thickness of atleast one of the plurality of second channel patterns in a directionperpendicular to a top surface of the substrate.
 9. The semiconductordevice according to claim 1, wherein the plurality of first channelpatterns each have substantially a same thickness in a directionperpendicular to a top surface of the substrate, and wherein at leastone of the plurality of second channel patterns has a differentthickness from a thickness of another channel pattern of the pluralityof second channel patterns in the direction.
 10. The semiconductordevice according to claim 9, wherein an uppermost one of the pluralityof second channel patterns has a different thickness from a thickness ofanother channel pattern of the plurality of second channel patternsunder the uppermost one of the plurality of second channel patterns inthe direction.
 11. The semiconductor device according to claim 1,wherein the first gate insulating pattern includes a material differentfrom that of the second gate insulating pattern.
 12. A semiconductordevice, comprising: first channel patterns on a substrate, the firstchannel patterns being spaced apart from each other in a first directionperpendicular to a top surface of the substrate; second channel patternson the substrate, the second channel patterns being spaced apart fromeach other in the first direction and spaced apart from the firstchannel patterns in a second direction parallel to the top surface ofthe substrate; a first gate structure extending in a third directionparallel to the top surface of the substrate and perpendicular to thesecond direction, the first gate structure enclosing a least a portionof each of the first channel patterns; a second gate structure extendingm the third direction, the second gate structure enclosing a least aportion of each of the second channel patterns and being spaced apartfrom the first gate structure in the second direction; a first epitaxialpattern at a first side of the first gate structure in the seconddirection, the first epitaxial pattern contacting a first end portion inthe second direction of each of the first channel patterns; a secondepitaxial pattern between a second side of the first gate structure inthe second direction and a first side of the second gate structure inthe second direction, the second epitaxial pattern contacting a secondend portion in the second direction of each of the first channelpatterns and a first end portion in the second direction of each of thesecond channel patterns; and a third epitaxial pattern at a second sideof the second gate structure in the second direction, the thirdepitaxial pattern contacting a second end portion in the seconddirection of each of the second channel patterns, wherein at least oneof the second channel patterns has a different thickness in the firstdirection from a thickness of another channel pattern of the secondchannel patterns in the first direction.
 13. The semiconductor deviceaccording to claim 12, wherein the first gate structure encloses acentral portion in the second direction of each of the first channelpatterns, and the second gate structure encloses a central portion inthe second direction of each of the second channel patterns, and whereinthe semiconductor device further comprises: first and second spacerscontacting opposite sidewalls, respectively, in the second direction ofthe first gate structure, the first and second spacers being disposedbetween the first channel patterns; and third and fourth spacerscontacting opposite sidewalls, respectively, in the second direction ofthe second gate structure, the third and fourth spacers being disposedbetween the second channel patterns.
 14. The semiconductor deviceaccording to claim 13, further comprising: fifth and sixth spacerscontacting opposite sidewalls, respectively, in the second direction ofthe first gate structure, the fifth and sixth spacers being disposed onan uppermost one of the first channel patterns; and seventh and eighthspacers contacting opposite sidewalls, respectively, in the seconddirection of the second gate structure, the seventh and eighth spacersbeing disposed on an uppermost one of the second channel patterns. 15.The semiconductor device according to claim 12, wherein the first gatestructure includes a first gate insulating pattern, a first gateelectrode, and a first hard mask sequentially stacked, and the secondgate structure includes a second gate insulating pattern, a second gateelectrode, and a second hard mask sequentially stacked, and wherein thefirst and second gate insulating patterns include different materialsfrom each other.
 16. The semiconductor device according to claim 12,wherein a first number of the first channel patterns stacked in thefirst direction is different from a second number of the second channelpatterns stacked in the first direction.
 17. The semiconductor deviceaccording to claim 12, further comprising: an insulating interlayer onthe substrate, the insulating interlayer covering the first and secondgate structures and the first to third epitaxial patterns; and first tothird contact plugs extending through the insulating interlayer andcontacting the first to third epitaxial patterns, respectively.
 18. Asemiconductor device, comprising: first channel patterns on a substrate,the first channel patterns being spaced apart from each other in a firstdirection perpendicular to a top surface of the substrate; secondchannel patterns on the substrate, the second channel patterns beingspaced apart from each other in the first direction and spaced apartfrom the first channel patterns in a second direction parallel to thetop surface of the substrate; a first gate structure extending in athird direction parallel to the top surface of the substrate andperpendicular to the second direction, the first gate structureenclosing a least a portion of each of the first channel patterns, andthe first gate structure including a first gate insulating pattern, afirst gate electrode, and a first hard mask sequentially stacked; asecond gate structure extending in the third direction, the second gatestructure enclosing a least a portion of each of the second channelpatterns and being spaced apart from the first gate structure in thesecond direction, and the second gate structure including a second gateinsulating pattern, a second gate electrode, and a second hard masksequentially stacked; a first epitaxial pattern at a first side of thefirst gate structure in the second direction, the first epitaxialpattern contacting a first end portion in the second direction of eachof the first channel patterns; a second epitaxial pattern between asecond side of the first gate structure in the second direction and afirst side of the second gate structure in the second direction, thesecond epitaxial pattern contacting a second end portion in the seconddirection of each of the first channel patterns and a first end portionin the second direction of each of the second channel patterns; and athird epitaxial pattern at a second side of the second gate structure inthe second direction, the third epitaxial pattern contacting a secondend portion in the second direction of each of the second channelpatterns, wherein the first and second gate insulating patterns includedifferent materials from each other.
 19. The semiconductor deviceaccording to chum 18, wherein a first number of the first channelpatterns stacked in the first direction is different from a secondnumber of the second channel patterns stacked in the first direction.20. The semiconductor device according to claim 18, wherein the firstgate structure encloses a central portion in the second direction ofeach of the first channel patterns, and the second gate structureencloses a central portion in the second direction of each of the secondchannel patterns, and wherein the semiconductor device furthercomprises: first and second spacers contacting opposite sidewalls,respectively, in the second direction of the first gate structure, thefirst and second spacers being disposed between the first channelpatterns; and third and fourth spacers contacting opposite sidewalls,respectively, in the second direction of the second gate structure, thethird and fourth spacers being disposed between the second channelpatterns.